1. LIGO-G020489-00-D Online Digital Signal Processing NSF Review, October 23, 2002 Daniel Sigg, LIGO Hanford Observatory

2. LIGO-G020489-00-D NSF Review2 Digital Feedback Systems  Length Sensing and Control  Mode cleaner length  DARM, CARM, MICH and PRC  MCL common mode  Alignment Sensing and Control  WFS1 to WFS5  QPDX and QPDY  Digital Suspension System  SOS: MC1, MC2, MC3, SM, MMT1, MMT2 and MMT3  LOS: RM, BS, ITMX, ITMY, ETMX, ETMY, FMX and FMY  Local damping and optical lever damping

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6. LIGO-G020489-00-D NSF Review6 Interface to Analog World  Input (16k and 2k)  Whitening (analog)  Anti-aliasing filter (analog)  Analog-to-digital converter  Anti-whitening (digital)  Output (16k and 2k)  Anti-dewhitening (digital)  Digital-to-analog converter  Anti-image filter (analog)  Dewhitening (analog)

7. LIGO-G020489-00-D NSF Review7 Standard Filter Module  Filter Module  10 sections w/ 10 SOS each (IIR up to 20 th order)  On-off at input and output  Gain & Input offset adjust  Output limiter & Output hold  Filter coefficients loaded on-the-fly  Filter sections  Can be turned on/off individually  Input switch: zero history, always on  Output switch: Immediate, ramp, zero-crossing, input-crossing  Diagnostics  Excitation point at input  Test points at input (before and after injection) and output  EPICS channels

8. LIGO-G020489-00-D NSF Review8 Standard Filter Module (2)  DSC: 27–33 filter modules/optic, 13–16 optics/ifo  LSC: 15 filter modules  ASC: 64 filter modules  Total: ~500 filter modules/ifo

9. LIGO-G020489-00-D NSF Review9 Foton – Filter Online Tool  Filter Design Tool w/ graphical user interface  Read and write coefficient files for online system  Design Methods:  ZPK: Zero-pole-gain  Resonant gain, Notch, Comb  Elliptic, Butterworth, Chebyshev type 1 and type 2  SOS and z-plane roots  Plotting:  Transfer function (Bode)  Step, impulse and ramp response  Pole and zero location (z- and s-plane)

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12. LIGO-G020489-00-D NSF Review12 DSC Status  ~2500 process variables in DSC  Check nominal settings  Nominal values and tolerances  Binary word and mask

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